<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<!-- 引入js文件 -->
	<script src="http://cdn.bootcss.com/jquery/2.1.4/jquery.min.js"></script>
</head>
<body>
<!-- 创建一个表单 -->
	<form action="2.php" method="post" enctype="multipart/form-data">
	<!-- <input type="file" name='icon'/><br/> -->
	<ul>
		<li>
			<input type="file" name="up[]"/>
			<!-- 通过js实现点击[+]增加文件域 -->
			<span onclick="cloneLi()">[+]</span>
		</li>
		</ul>
		<br/>
		<input type="submit">
	</form>
	<script>
		function cloneLi()
		{
			var li = $('li').eq(0).clone();
			$("ul").append(li);
		}
	</script>
</body>
</html>